This invention relates to a method and an apparatus for inspecting the sidewalls of bottles.
It is necessary to inspect glass bottles containing liquors, beverages, foods, etc. for defects whether the bottles are newly made or have been recovered. The bottles are inspected at various parts, i.e., the bodies or sidewalls, bottoms, tops of the mouths and the threaded bottle necks. Among these parts, the sidewalls tend to have defects such as foreign matters causing food sanitary problems, checks, cracks, scraches, seeds, blisters, etc., possibly causing accidental bottle breakages. Accordingly it is necessary to accurately identify and these defects to remove defective bottles with these defects. To this end there has been proposed a method for obtaining an image of light transmitted through a transparent or opaque bottle to detect defects based on a darkness distribution of the transmitted light image.
A problem with this method is that light-blocking defects, such as foreign matters, smears on the sidewall of a bottle, can be detected, based on a darkness distribution in an image of light transmitted through the sidewall. However based only on the darkness distribution, it is difficult to detect refractive defects, such as seeds, blisters, streaks, rumples, etc.